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I'm building my first fixed gear bike and I'm nearly finished, I just have to tighten up my crank bolt and wrap my handle bars. The thing is, the crank arm seems to wobble a lot and idk what to do. I've already tried tightening it some more, but I don't think that'll help.

Bottom bracket shell: 68mm

Bottom bracket: SRAM GXP's

Crankset: SRAM Omniums

video showing wobble:

https://imgur.com/f26nppn

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    Stupid question: Is it the crank arm wobbling, or is the shaft rattling in the BB? If the crank arm itself is wobbling this is usually due to a used arm that was ridden loose. – Daniel R Hicks Dec 21 '19 at 3:10
  • not exactly sure what you're asking, but the arm itself is fine i think, i think its more the spindle wobbling in the BB – user46474 Dec 21 '19 at 3:16
  • Did you add the 2.5mm spacers on each side of the BB? Check out SRAM service manual: cdn.sram.com/sites/default/files/techdocs/… – P. Barney Dec 21 '19 at 4:53
  • Is that BB new or used? – whatsisname Dec 21 '19 at 15:58
  • @whatsisname it came included with my omniums, it shouldnt be used. – user46474 Dec 21 '19 at 18:09
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I believe there can be an issue with play in GXP cranks. The play in the bearings is taken up by the non drive side crank arm sliding up along the splined taper as the bolt is done up and compressing the wave washer in the drive side. The bolt can be tightened up to the correct torque but there is still lateral play.

Definitely check you have the spacers and wave washer installed correctly. You may need an additional shim to take up the play.

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  • @ Argenti Apparatus @Nathan Knutson What about insufficient bearing preload? Is it like the Hollowtech 2 system where left crank arm has a threaded preloader where a crankarm "fixing bolt" used to be? – Jeff Dec 29 '19 at 13:00
  • @Jeff GXP works differently to HT because apparently Shimano patented their system. Bearing preload on the drive side is accomplished by the wave washer, there isn't any preload on the non-drive side. Hambini did a vid on his youtube channel about this (note if you are going to look this up and watch: he swears and cusses alot.) – Argenti Apparatus Dec 29 '19 at 13:25

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